Orthodontic appliance



FIG. 1 is a bottom perspective view of an orthodontic appliance showing my new design;

FIG. 2 is a bottom plan view thereof;

FIG. 3 is a top plan view thereof;

FIG. 4 is a side elevational view thereof, the opposite side being a mirror image of that shown;

FIG. 5 is a front elevational view thereof; and

FIG. 6 is a rear elevational view thereof. 

The ornamental design for an orthodontic appliance, as shown and described. 